1. Technical Field of the Invention
The present invention relates to an apparatus and method for treating snoring, with or with without sleep apnea. More specifically, the invention relates to an extra-oral method of providing mandibular advancement, a method shown to be effective in the treatment of snoring.
2. Background of the Invention
The term snoring generally refers to a rough or hoarse sound that arises from a person's mouth while sleeping. The problems caused by snoring are both social, affecting those who sleep with or near the person snoring, and medical, sometimes signaling a more profound problem known as sleep apnea.
FIG. 1B is a view looking into the mouth and demonstrates some of the portions of the mouth and pharynx (throat) that are involved in snoring. The tongue 103 takes up the visible area in the lower part of the mouth. The palate is the roof of the mouth and includes the hard palate 107, in which tissue closely overlies bone, and the soft palate 108, which has no underlying bones. The pendulous structure on the lower edge of the soft palate is the uvula 104. Two “arches” across the entrance to the throat are seen; the muscles that form these arches are the palatoglossus 110, which joins the palate and the tongue, and the palato-pharyngeus 112, which joins the palate and the pharynx. The back of the pharynx 114 is seen behind the uvula, while the palatine tonsils 116 are seen bilaterally between the two arches. All of these structures, with the exception of the hard palate, are unsupported by bone along much of their length. During waking hours, normal tension in the muscles of the mouth and pharynx maintains a smooth airway in which air flows quietly, but as we fall asleep, these muscles become deeply relaxed. This can cause narrowing of the pharyngeal airway, which in turn causes turbulent airflow. This turbulent airflow vibrates the soft parts of the pharyngeal passage, causing the phenomenon we know as snoring. In children, enlarged tonsils or adenoids that obstruct the pharyngeal passageway can cause snoring. In adults, the contributing factors generally include a lack of muscle tone in the muscles of the airway, the consumption of alcohol or drugs, which causes a deeper relaxation, and smoking, which irritates the mucus membranes of the upper airway causing swelling and increased mucus production. Anatomical features can also play a part, such as a short neck or receding jaw line.
FIG. 1A shows a cross-section through the midline of a human head, showing the maxilla (upper jaw) 120, the mandible (lower jaw) 122, nasal airway 101, oral airway 102, tongue 103, hard palate 107, soft palate 108, uvula 104 and rear wall of the pharynx 114. Note especially that the tongue 103 has no fixed attachment other than to the back side of the mandible 122. (The tongue is also attached to the small hyoid bone 124, but this bone is not fixed.) This drawing makes it clear how little space exists between the rear wall of the pharynx 114 and the tongue 103, soft palate 108, and uvula 104. In a wakeful person, normal muscle tension maintains both the oral airway 102 and the posterior portions of the nasal airway 101 open to the trachea 107, and thus to the lungs. However, it is not difficult to imagine from this illustration what can happen when a person sleeps, especially if they sleep on their back. Given the effects of muscle relaxation and gravity, both the soft palate 108 and the rear portion of the tongue 103 can easily fall against the back of the pharynx 105. Depending on the degree of blockage, there can be simple snoring or a momentary, total blockage of the airflow, known as obstructive sleep apnea. Obstructive sleep apnea is a potentially very serious condition. The oxygen starvation it induces can cause the person to partially awaken in order that muscle tension can open the airway and get air into their lungs. Apnea patients may experience 30 to 300 obstructed events per night, and many spend as much as half their sleep time with blood oxygen levels below normal. During their obstructive episodes, the heart must pump harder to circulate the blood faster. This condition can cause excessive daytime sleepiness, irregular heartbeats, and after many years it leads to elevated blood pressure and heart enlargement. Persons with obstructive sleep apnea may spend little of their nighttime hours in the deep sleep stages that are essential for a good rest. Therefore, they awaken un-refreshed and are sleepy much of the day. They can even fall asleep while driving or performing other activities.
The prior art is replete with different efforts to attempt to control snoring and sleep apnea. Among the less intrusive methods of preventing snoring are special pillows, nasal strips, wrist alarms and chemical sprays. The shaped pillows have been designed to realign the back and spine and to relieve muscle stress during sleep, while the adhesive nasal strips help open the nostrils of a sleeper to improve breathing. Wrist alarms are designed to detect the noise of snoring and to partially arouse a sleeper, ideally to prompt the person to move to a less troublesome position. Chemical sprays contain oils and glycerin that can coat the mucus membranes of the pharyngeal passageway and decrease the noise associated with snoring. For mild cases, these remedies may be all that is necessary, or relief may be found by reducing triggering factors, i.e., losing weight, stopping smoking, and/or decreasing alcohol consumption. However, for more severe cases, the easy solutions usually do not solve the problem. The sleeper can shift and move off of a pillow, while the nasal strips will not help an obstruction in the pharynx. A wrist alarm does not allow the wearer to get a good night's sleep and chemical sprays can wear off in a few hours.
For more serious cases, and especially where sleep apnea is involved, the options have included Continuous Positive Airway Pressure (CPAP), mouth guards that reposition the lower jaw, and surgery.
CPAP uses a small compressor to create and maintain a positive pressure in the airway at all times by air forced through a nasal mask or nasal pillows. This positive pressure is enough to hold the airway open. The downside is that the mask must be firmly held in place on the patient's nose, while tubing ties the sleeper to the compressor. FIG. 2 shows a sleeping person wearing a nasal pillow connector 210 with attached tubing 212 that leads to a CPAP machine (not specifically shown). Various straps 214 hold the nasal pillows in place and the mouth closed. The masks or nasal pillows can cause skin irritation and pressure points, which in turn can be painful and can make falling asleep difficult. Although CPAP works well in persons who can tolerate it, not everyone can.
Surgical intervention is generally aimed at removing excess tissue in the pharynx or soft palate, such as tonsils, adenoids, and portions of the soft palate or uvula. Newer procedures have included a process to stiffen the tissue of the soft palate, so that it is less apt to form an obstruction.
At least one surgical procedure has taken a different tack to correct snoring, as is demonstrated in FIG. 3. An incision is made adjacent the anterior mandible 300, a portion of which is shown with the six anterior teeth 310. A small rectangular section 302 of the mandible is sectioned and pulled forward, with muscles of the tongue (the attachment can be seen in FIG. 1B) still attached. The section 302 is then rotated 90° and fixed in place. Because the muscles remain attached to the bony section, the body of the tongue is pulled to a more anterior position by several millimeters. This prevents the tongue from being able to move as far back into the pharynx as it was previously able to, increasing the airway and decreasing or eliminating snoring and apnea. While this surgery avoids the problem of the tongue blocking the airway, many sufferers consider surgery a rather drastic step, as it is often both expensive and painful.
Special dental mouthpieces can act in much the same way as the surgical procedure described above, but without the need to cut tissue. These mouthpieces reposition the lower jaw to a more forward position during sleep, preventing the tongue from obstructing the pharynx. The following figures demonstrate this repositioning of the bony structures of the jaws.
FIG. 4A is a model of a human skull, showing the relationship of the mandible 410 to the skull 400, especially to the temporal bone 406 that makes up the area around the ear. The head 412 of the mandible 410 sits in a bowl-shaped socket 408 of the temporal bone 406, forming the temporomandibular joint or TMJ. The head of the mandible 410 is separated from the temporal bone by a thin disk of cartilage and held in place by muscles and ligaments. Because of these unique structures, the TMJ allows much more movement than just the swinging action of a hinge joint. It allows the mandible to move forward and backwards several millimeters and allows the head 412 of the mandible 410 on one side, e.g., the left, to rotate while the head 412 of the mandible 410 on the other (right) side moves outward and forward, causing the jaw to move to the left, as in chewing. In normal daily activities, such as speech and mastication, the position of the mandible is determined not only by the activity of the muscles and TMJ, but also by the position and interaction of the teeth. However, when the person is sleeping, the mouth is generally open with the teeth disengaged, and the musculature and joint structure determine the position. For a person lying on their back, the mandible can relax into its most posterior position, allowing maximal contact between the posterior tongue and the nearby soft structures.
The oral appliances used for mandibular advancement position the mandible forward during sleeping, as shown in FIG. 4B. Although the differences are somewhat subtle, note that in the normal dentition shown, the lower incisors 420 (front teeth) move in front of the upper incisors 422, while the head 412 of the mandible 410 rides up the anterior side of the socket 408 of the temporal bone. This movement pulls the tongue forward, maintaining a clear space behind the tongue for breathing.
Studies have shown that mouthpieces providing mandibular advancement are as effective as CPAP in maintaining an open airway. This has been verified in unconscious patients whose musculature had been paralyzed, confirming that this is due to anatomical relationships and that the results do not require muscle activity. There are a number of versions of this type of mouthpiece. Some are custom-made, while others are of the “boil and bite” variety used in many school athletic programs. Although mandibular advancement was originally not well accepted by the medical community, the results of scientific studies are bringing this methodology into greater favor. However, as with CPAP, even when the devices work, many patients cannot tolerate the intra-oral devices. In other cases, the patient may tolerate the mouthpiece, only to find that the pressure exerted on the teeth by the appliance causes the teeth to shift out of position.
As an example of this problem, one of the inventors of the present application was diagnosed with severe sleep apnea and placed in an intra-oral device to correct the problem. However, after four years of using the intra-oral device, he was unable to eat solid food and was rapidly losing weight because of it. An oral examination revealed that his anterior teeth touched, but his posterior teeth did not. It was realized at that point that the pressure of the oral appliance had caused his lower anterior teeth to rotate to a more forward position, while the upper anterior teeth rotated to a more posterior position, as shown in FIG. 5.
Thus, despite the large number of devices and methods for the treatment of snoring, there remains a need for an anti-snoring device and/or method that maintains an open pharyngeal airway, is well tolerated, and does not exert pressure on the teeth.